package utils;

/*
 **************************************************************************
 *                                                                        *
 *          General Purpose Hash Function Algorithms Library              *
 *                                                                        *
 * Author: Arash Partow - 2002                                            *
 * URL: http://www.partow.net                                             *
 * URL: http://www.partow.net/programming/hashfunctions/index.html        *
 *                                                                        *
 * Copyright notice:                                                      *
 * Free use of the General Purpose Hash Function Algorithms Library is    *
 * permitted under the guidelines and in accordance with the most current *
 * version of the Common Public License.                                  *
 * http://www.opensource.org/licenses/cpl.php                             *
 *                                                                        *
 **************************************************************************
 */

public class GeneralHashFunctionLibrary {

    public long RSHash(String str) {
	int b = 378551;
	int a = 63689;
	long hash = 0;

	for (int i = 0; i < str.length(); i++) {
	    hash = hash * a + str.charAt(i);
	    a = a * b;
	}

	return hash;
    }

    /* End Of RS Hash Function */

    public long JSHash(String str) {
	long hash = 1315423911;

	for (int i = 0; i < str.length(); i++) {
	    hash ^= ((hash << 5) + str.charAt(i) + (hash >> 2));
	}

	return hash;
    }

    /* End Of JS Hash Function */

    @SuppressWarnings("cast")
    public long PJWHash(String str) {
	long BitsInUnsignedInt = (long) (4 * 8);
	long ThreeQuarters = (long) ((BitsInUnsignedInt * 3) / 4);
	long OneEighth = (long) (BitsInUnsignedInt / 8);
	long HighBits = (long) (0xFFFFFFFF) << (BitsInUnsignedInt - OneEighth);
	long hash = 0;
	long test = 0;

	for (int i = 0; i < str.length(); i++) {
	    hash = (hash << OneEighth) + str.charAt(i);

	    if ((test = hash & HighBits) != 0) {
		hash = ((hash ^ (test >> ThreeQuarters)) & (~HighBits));
	    }
	}

	return hash;
    }

    /* End Of P. J. Weinberger Hash Function */

    public long ELFHash(String str) {
	long hash = 0;
	long x = 0;

	for (int i = 0; i < str.length(); i++) {
	    hash = (hash << 4) + str.charAt(i);

	    if ((x = hash & 0xF0000000L) != 0) {
		hash ^= (x >> 24);
	    }
	    hash &= ~x;
	}

	return hash;
    }

    /* End Of ELF Hash Function */

    public long BKDRHash(String str) {
	long seed = 131; // 31 131 1313 13131 131313 etc..
	long hash = 0;

	for (int i = 0; i < str.length(); i++) {
	    hash = (hash * seed) + str.charAt(i);
	}

	return hash;
    }

    /* End Of BKDR Hash Function */

    public long SDBMHash(String str) {
	long hash = 0;

	for (int i = 0; i < str.length(); i++) {
	    hash = str.charAt(i) + (hash << 6) + (hash << 16) - hash;
	}

	return hash;
    }

    /* End Of SDBM Hash Function */

    public long DJBHash(String str) {
	long hash = 5381;

	for (int i = 0; i < str.length(); i++) {
	    hash = ((hash << 5) + hash) + str.charAt(i);
	}

	return hash;
    }

    /* End Of DJB Hash Function */

    public long DEKHash(String str) {
	long hash = str.length();

	for (int i = 0; i < str.length(); i++) {
	    hash = ((hash << 5) ^ (hash >> 27)) ^ str.charAt(i);
	}

	return hash;
    }

    /* End Of DEK Hash Function */

    public long BPHash(String str) {
	long hash = 0;

	for (int i = 0; i < str.length(); i++) {
	    hash = hash << 7 ^ str.charAt(i);
	}

	return hash;
    }

    /* End Of BP Hash Function */

    public long FNVHash(String str) {
	long fnv_prime = 0x811C9DC5;
	long hash = 0;

	for (int i = 0; i < str.length(); i++) {
	    hash *= fnv_prime;
	    hash ^= str.charAt(i);
	}

	return hash;
    }

    /* End Of FNV Hash Function */

    public long APHash(String str) {
	long hash = 0xAAAAAAAA;

	for (int i = 0; i < str.length(); i++) {
	    if ((i & 1) == 0) {
		hash ^= ((hash << 7) ^ str.charAt(i) * (hash >> 3));
	    } else {
		hash ^= (~((hash << 11) + str.charAt(i) ^ (hash >> 5)));
	    }
	}

	return hash;
    }
    /* End Of AP Hash Function */

}
